When manufacturing printed circuits, hybrid circuits or especially integrated circuits, a master mask is used for projecting the pattern of the circuit through an optical system. This may be, for example, a reducing system. The projection is made onto a photo-sensitive layer of a substrate or wafer. This layer is subsequently chemically and physically treated in order to obtain the desired circuits. Conventionally, there are projected onto the photo-sensitive layer several equal images of the mask in a side-by-side relationship to produce a corresponding number of circuits from one substrate or wafer. To this end, there is needed a stepwise relative movement of the projected image and the wafer, and this normally is done by a stepwise displacement of the wafer in its plane. The wafer is therefore mounted on a cross slide system which--after one image has been exposed thereonto--needs to be moved by one step (for example of the order of 10 mm) to project the pattern of the mask onto the adjacent area of the wafer. The individual steps must be carried out very quickly and with the highest precision because tolerances of more than 1.mu. would cause a spoilage.
Machines of this kind have been described, for example, in U.S. Pat. Nos. 3,632,074 or 3,695,758 and in the applications Ser. Nos. 247,530; 247,614 and 247,639. Particularly in the DE-OS 2,942,388 the problems of positioning a wafer with the necessary precision have been described in detail.
With machines of relative low throughputs heretofore in use (as described in the above-mentioned references) achievement of such a precision posed no difficulty.
However, in order to obtain a higher efficiency it would be desirable to increase the production rate, and therefore the velocity of each stepwise displacement. It is, of course, to be understood that with an increasing velocity also higher accelerations and especially decelerations will occur. These sudden decelerations at the end of each step cause oscillations of the cross slide system, the amplitudes of which can exceed the admissable tolerances considerably, and consequently lead to greater spoilage due to image blurring. Thus the prior art evidences that it was not readily possible to raise the efficiency of such machines.
It is accordingly an object of the instant invention to provide measures for an increased efficiency of circuit printing machines.
It is furthermore an object of the invention to displace a cross slide system at higher speeds than has been possible heretofore without, however, increasing the spoilage.
Another object of this invention is an improved dampening device for such machines, in order to provide a higher displacement velocity of the wafer, and hence a decreased oscillation time.